Method and apparatus for improving the temperature stability and minimizing the noise of the environment that encloses an interferometric measuring system

Abstract

Disclosed herein is a method and system for providing environmental control for a vibration sensitive system such as an interferometric measurement system, while minimizing acoustic noise during data acquisition.

With this in mind, we claim: 
     
       1. An apparatus for providing environmental control for a vibration sensitive measurement system including a metrology instrument comprising:
 an enclosure enclosing said vibration sensitive measurement system, said enclosure having a thermally stable mini environment within substantially the entire enclosure; 
 said enclosure having forced air circulation within provided by an air circulation unit, said air circulation unit including a fan having a fan speed; 
 a controller configured to control said air circulation unit and said fan speed; 
 said controller configured to set the fan speed at a very low speed or zero speed during data acquisition times, and to maintain the fan speed at a fast speed during non-data acquisition times, thereby reducing or eliminating measurement error of said vibration sensitive measurement system resulting from fan-induced acoustic noises and vibration. 
 
     
     
       2. The apparatus of  claim 1 ,
 further including means for controlling temperature within said enclosure. 
 
     
     
       3. The apparatus of  claim 2 ,
 wherein said means for controlling temperature within said enclosure includes: 
 a heating element within said enclosure; 
 wherein said controller is further configured to control said heating element; and 
 further including at least one temperature sensor within said enclosure, said at least one temperature sensor providing temperature feedback to said controller. 
 
     
     
       4. The apparatus of  claim 3 , wherein at least one said temperature sensor is mounted on said metrology instrument. 
     
     
       5. The apparatus of  claim 3 , further including a cooling element within said enclosure, wherein said controller further controls said cooling element. 
     
     
       6. The apparatus of  claim 1 , wherein said fan is proximal an opening to said enclosure. 
     
     
       7. The apparatus of  claim 1 , wherein said fan is in a position removed from an opening to said enclosure, and wherein a duct brings air from said fan into said enclosure. 
     
     
       8. The apparatus of  claim 1 , wherein said very low fan speed is sufficiently low to maintain acoustic noise and system vibration below user-determined levels. 
     
     
       9. The apparatus of  claim 1 , wherein said fast fan speed is a sufficiently high speed to provide user-determined sufficient air circulation and temperature stability. 
     
     
       10. The apparatus of  claim 1 , wherein said vibration sensitive measurement system is an interferometric measurement system.